Super absorbent distribution system design for homogeneous distribution throughout an absorbent core

ABSTRACT

A super absorbent distribution system for homogenous distribution throughout an absorbent core is disclosed. A super absorbent material is injected into a stream of absorbent fluff at an opposite direction to that of the stream of absorbent fluff. The super absorbent is blasted into the peak and outer surface of a cone shaped super absorbent barrier. The oncoming absorbent fluff also contends with a similarly shaped absorbent fluff barrier. The super absorbent material slows down as it hits the super absorbent barrier and oncoming fluff, then stops, then reverses direction and flows with the absorbent fluff as a homogenous distribution of super absorbent material and absorbent fluff. The combination of super absorbent material and absorbent fluff may encounter baffle members to further distribute the super absorbent material and absorbent fluff.

RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/563,517, filed 19 Apr. 2004, and entitled “SuperAbsorbent Distribution System Design for Homogeneous DistributionThroughout an Absorbent Core.”

BACKGROUND OF THE INVENTION

This invention relates to a method and apparatus for forming anabsorbent core having a multiplicity of components. More particularly,the present invention relates to a method and apparatus for producing ahomogeneous distribution of super absorbent material throughout anabsorbent core.

Absorbent articles including bandages, disposable diapers, and sanitarynapkins, generally include an absorbent core that has a multiplicity ofcomponents so as to improve the article's absorption and retentioncharacteristics. These absorbent cores have had their total absorbencyimproved greatly by the addition of super absorbent material to thecommonly used absorbent fibrous materials.

Typically, the absorbent fibrous material is composed of cellulosewadding or cellulosic wood pulp material commonly referred to as“fluff”, although a mixture of natural and synthetic fibers is withinthe scope of the invention. An absorbent core composed of wood pulpfluff is typically formed by employing conventional air layingtechniques.

The ability of these absorbent cores to manage the typical surges ofliquid flow is heavily dependent on the proper distribution of superabsorbent material within the absorbent fluff. When most super absorbentmaterials absorb aqueous fluids, they swell substantially, often todouble their dry dimensions or more at saturation. As these superabsorbent materials absorb fluid and swell, they generally become agelatinous mass. If the super absorbent material is in a particulateform and the particles are close to one another, they can create aphenomenon known as “gel-blocking,” wherein the saturated blocks ofsuper absorbent material inappropriately provide a barrier to additionalsurges of liquid.

Thus, for maximum effectiveness of the super absorbent material,absorbent structures which include such materials in particulate formpreferably maintain separation of the particles from one another topermit maximum absorption and swelling without allowing the particles tocoalesce and form the gel barrier.

To avoid this barrier and to optimize performance, various modes ofdistribution of super absorbent material throughout the absorbent corehave been tried. Layering and blending the super absorbent materialwithin the absorbent core make up the principle two modes. Examples ofgenerally layered applications can be seen in U.S. Pat. No. 4,551,191issued Nov. 5, 1985 to Kock et al. and U.S. Pat. No. 6,416,697 issuedJul. 9, 2002 to Venturino et al. In this method, super absorbentmaterial is commonly distributed onto a moving porous web. Examples ofblended applications can be seen in U.S. Pat. No. 4,764,325 issued Aug.16, 1988 to Angstadt and U.S. Pat. No. 4,927,582 issued May 22, 1990 toBryson. In a blended application, the super absorbent material first ismixed with the absorbent fluff. Then the mixture is laid down creatingthe absorbent structure.

Super absorbent material typically has the consistency of sand, whileabsorbent fluff is more fibrous, and tends to knit together. Highconcentrations of super absorbent material, if not distributed amongstthe fluff fibers, performs poorly and tends to fall out of the productduring manufacturing—a loss of investment.

Manufacturers have attempted to optimize distribution of the superabsorbent material in order to get the most “bang for the buck” out oftheir investment. As well, optimizing the distribution and eliminatinglocalized buildup of super absorbent material can improve the feel ofthe article on the user. For example, eliminating a localized buildup ofsuper absorbent material along an inner layer of a diaper can eliminatethe gritty feel of the super absorbent material next to the baby's skin,making for a much happier baby and a more effective diaper.

Likewise, there has been a trend in reducing the bulk of diapers, inattempts to make them more like underwear and to take up less shelfspace in retailer's outlets. Generally, the thinner the diaper, thehigher the concentration of super absorbent material required to producethe same level of absorbency. High levels of super absorbent material,however, tend to be more difficult to control and to maintain inposition.

In solving these problems, the most friendly application of superabsorbent material would seem to be a completely uniform (homogeneous)distribution, with no noticeable local concentrations of super absorbentmaterial. To achieve homogenous blending, it is necessary to add thesuper absorbent material to the main air stream that carries theabsorbent fluff to the deposition molds that form the cores.

Super absorbent material, however, has entirely different behavior fromfluff fibers. It has a much higher density (thus a higher inertia) anddoes not easily follow the fluff fibers along their turbulent paths totheir final, intended resting place. Once it has been imparted with avelocity, the super absorbent material tends to behave more like abullet than a leaf in the wind. This all makes it difficult to mix thesuper absorbent material uniformly with the absorbent fluff. It is aproblem of uniformly blending two very different components.

The prior art super absorbent distribution techniques such as thoseherein described earlier have made attempts in providing substantiallyuniform distribution of the particulate super absorbent material.However, none of the foregoing appears to have adequately understood andaddressed the problems associated with the entirely different behaviorsof the super absorbent material and the fluff fibers.

Because of the foregoing deficiencies in the art, an object of thepresent invention is to provide a method and apparatus that solves theseproblems by making the distribution of the super absorbent materialwithin the fluff fibers more uniform. Homogeneous distribution can beachieved by essentially altering the behavior of the super absorbentmaterial to make its behavior more closely replicate that of theabsorbent fluff in which it must uniformly mix.

SUMMARY OF THE INVENTION

The present invention comprises a unique method and apparatus forinjecting super absorbent material into a main fluff-carrying airstream. Specifically, the present invention provides a novel superabsorbent distribution system for homogenous distribution of the superabsorbent material throughout the absorbent fluff. The super absorbentmaterials to be used with the present invention may be manufactured froma variety of materials. A wide variety of super absorbent materials areknown to those skilled in the art. See, for example, U.S. Pat. No.4,076,663 issued Feb. 28, 1978 to Masuda et al, U.S. Pat. No. 4,286,082issued Aug. 25, 1981 to Tsubakimoto et al., U.S. Pat. No. 4,062,817issued Dec. 13, 1977 to Westerman, and U.S. Pat. No. 4,340,706 issuedJul. 20, 1982 to Obayashi et al. Additionally, the super absorbentmaterials to be used with the present invention may be of varying commondimensions.

The invention uses a unique method and apparatus for injecting superabsorbent material into the main fluff-carrying air stream. Theinvention directs the super absorbent material upstream into theoncoming path of the absorbent fluff, but first impinges the stream ofsuper absorbent material against the peak of a cone-shaped barrier,which flares the stream of super absorbent material particles outward,causing them to slow down and to reverse their direction, joining theabsorbent fluff stream at a point and at a velocity which carries thesuper absorbent material along, as though they were part of the samestream of fluff fibers. The cone-shaped barrier also distributes thesuper absorbent material with relative uniformity, thereby enhancing theobjective of achieving homogenous distribution.

In addition to the reverse flow insertion of the stream of superabsorbent material, an additional component in the operation of thisinvention includes the addition of “speed bumps,” which may be bafflemembers inserted to disrupt the continuity of the air stream, furtherdistributing the super absorbent material and absorbent fluff throughoutthe fiber lay-down process.

Again, an objective of this invention is to inject the stream of superabsorbent material particles into the stream of air-entrained flufffibers so that they may most naturally assume the velocity andtrajectory of the fluff fibers. The effect is achieved as the particlesof super absorbent material are distributed with relative uniformitythroughout the absorbent pad.

It is another object of the present invention to provide an apparatusfor and method of making airlaid absorbent cores having discreteparticles of super absorbent material homogenously dispersed throughoutthe absorbent core.

It is a further object of the present invention to provide an apparatusfor and method of making absorbent cores having a multiplicity ofcomponents.

It is also an object of the present invention to provide an apparatusfor and method of making an absorbent core having a multiplicity ofcomponents, at least one of the components containing a particularamount of discrete particles of a super absorbent material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a distribution system that embodies thepresent invention.

FIG. 2 is a side elevation view of the distribution system shown in FIG.1, showing the injection of super absorbent material into the absorbentfluff air stream, and the resulting homogenous distribution of superabsorbent material and absorbent fluff.

FIG. 3 is a top plan view of the distribution system shown in FIG. 2.

FIG. 4 is a top plan view of the diffuser conduit assembly of thedistribution system shown in FIG. 1.

FIG. 4 a is a front view of a preferred embodiment of a fluff barrier.

FIG. 5 is a side elevation view of the diffuser conduit assembly shownin FIG. 4.

FIG. 6 is a front elevation view of the diffuser conduit assembly shownin FIG. 4.

FIG. 7 is a perspective view of an alternative embodiment of thedistribution system shown in FIG. 1, wherein the diffuser housing istubular in shape.

FIG. 8 is a top plan view of the diffuser conduit assembly for thealternative embodiment of the distribution system shown in FIG. 7,wherein the mounting plate is arced.

FIG. 9 is a side elevation view of the diffuser conduit assembly for thealternative embodiment of the distribution system shown in FIG. 7,wherein the mounting plate is arced.

FIG. 10 is a front elevation view of the diffuser conduit assembly forthe alternative embodiment of the distribution system shown in FIG. 7,wherein the mounting plate is arced.

FIG. 11 is a top plan view of an alternative embodiment of a diffuserconduit assembly, wherein the diffuser conduit extends through themounting plate at a predetermined angle.

FIG. 12 is a side elevation view of the alternative embodiment of thediffuser conduit assembly shown in FIG. 11, wherein the diffuser conduitextends through the mounting plate at a predetermined angle.

FIG. 13 is a front elevation view of the alternative embodiment of thediffuser conduit assembly shown in FIG. 11, wherein the diffuser conduitextends through the mounting plate at a predetermined angle.

FIG. 14 is a perspective view of an alternative embodiment of a diffuserconduit assembly, wherein the diffuser conduit assembly is essentiallylinear and enters the diffuser housing at a curved portion of thediffuser housing.

FIG. 15 is a perspective view of an alternative embodiment of thedistribution system of FIG. 1, wherein the diffuser housing includes anincrease in cross sectional flow area and a decrease in cross sectionalflow area.

FIG. 16 is a perspective view of an alternative embodiment of thedistribution system of FIG. 7, wherein the diffuser housing includes anincrease in cross sectional flow area and a decrease in cross sectionalflow area.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Although the disclosure hereof is detailed and exact to enable thoseskilled in the art to practice the invention, the physical embodimentsherein disclosed merely exemplify the invention which may be embodied inother specific structure. While the preferred embodiment has beendescribed, the details may be changed without departing from theinvention.

Referring to the drawings, wherein like numerals represent like partsthroughout the views, there is generally designated at 20 a distributionsystem according to the present invention. As seen particularly in FIGS.1 and 2, the distribution system 20 includes a diffuser housing 30 and adiffuser conduit assembly 100 for homogenous mixing of super absorbentmaterial 22 and absorbent fluff 26.

The diffuser housing 30 preferably comprises a top wall 40, a bottomwall 50, a first side wall 60, and a second side wall 70. The top wall40 includes an inside surface 42 and an outside surface 44. The bottomwall 50 also includes an inside surface 52 and an outside surface 54.The first side wall 60 includes an inside surface 62 and an outsidesurface 64. The second side wall 70 also includes an inside surface 72and an outside surface 74. The diffuser housing 30 also may include aninlet end 32 and an outlet end 34.

As further illustrated in the view of FIGS. 1 and 2, the distributionsystem 20 includes a diffuser conduit assembly 100 coupled to thediffuser housing 30. Disposed within any of the top wall 40, bottom wall50, first side wall 60, or second side wall 70 is a diffuser conduitassembly aperture 80. Diffuser housing mounting hole apertures 82preferably are positioned around the diffuser conduit assembly aperture80 in order to couple the aforementioned diffuser conduit assembly 100to the diffuser housing 30, by way of bolt and nut fasteners (notshown), although it is within the scope of the invention to couple thediffuser conduit assembly 100 to the diffuser housing 30 by otherconventional means such as welding or riveting.

As best seen in FIG. 1, the diffuser conduit assembly 100 preferably iscoupled to the diffuser housing 30 and may be partially disposed withinthe diffuser housing 30. In a preferred embodiment, the diffuser conduitinlet end 104 partially extends outside the diffuser housing 30 when thediffuser conduit assembly 100 is attached to the diffuser housing 30.

Now referring to FIGS. 4, 5, and 6, the diffuser conduit assembly 100preferably comprises a diffuser conduit 102 with an inlet end 104 and anoutlet end 106. The diffuser conduit 102 may also include an arc shapedbend 108 and a venturi 110 (shown best in FIG. 5), the venturi 110 beingpreferably located nearer the outlet end 106 than the inlet end 104. Thediffuser conduit venturi 110 accelerates the super absorbent material 22before it is injected into the oncoming flow path 28 of the absorbentfluff 26 (shown in FIGS. 2 and 3).

Coupled to the outlet end 106 of the diffuser conduit 102 are preferablythree support rods 112, although more or less support rods 112 may beused and remains within the scope of the invention. The support rods 112have a first end 114 and a second end 116, wherein the second end 116 iscoupled to the diffuser conduit 102.

As best seen in FIGS. 4, 4 a, and 5, coupled to the first end 114 of thesupport rods 112 is preferably a cone shaped super absorbent barrier120. Facing toward the outlet end 106 of the diffuser conduit 102, thecone shaped barrier 120 includes a peak 122 and an outer surface 124.The outer surface 124 includes a predetermined outer surface height H1.The cone shaped super absorbent barrier 120 also includes a base 126,having a base diameter D1, positioned at an opposite end to that of thepeak 122. The peak 122 of the cone shaped super absorbent barrier 120 ispreferably positioned at a predetermined distance X away from the outletend 106 of the diffuser conduit 102.

The cone shaped super absorbent barrier 120 has coupled to its base 126a similarly shaped cone shaped fluff barrier 140. In the preferredembodiment, the cone shaped fluff barrier 140 is a mirror image of thecone shaped super absorbent barrier 120. The cone shaped fluff barrier140 also includes a peak 142 and an outer surface 144. The outer surface144 includes a predetermined outer surface height H2. The cone shapedfluff barrier 140 also includes a base 146, having a base diameter D2,positioned at an opposite end to that of the peak 142. The peak 142 ofthe cone shaped fluff barrier 140 faces away from the outlet end 106 ofthe diffuser conduit 102.

Referring now to FIG. 4, also included with the diffuser conduitassembly 100 may be a mounting plate 160. The mounting plate 160 has afirst side 162 and a second side 164. A plurality of apertures 166 aredisposed within the mounting plate 160 in order to secure the mountingplate 160 to the diffuser housing 30 using a nut and bolt configuration(not shown) or other conventional means.

Referring now to FIG. 6, a front elevation view of the diffuser conduitassembly 100 is shown, correlating to FIG. 4.

As viewed in FIG. 7, in an additional alternative embodiment, thedistribution system disclosed may include a tubularly shaped diffuserhousing 230. The tubular diffuser housing 230 preferably includes aninlet end 232 and an outlet end 234. The tubular housing 230circumferential wall 240 comprises an inside surface 242 and an outsidesurface 244. Disposed within the circumferential wall 240 may be adiffuser conduit assembly aperture 280 and a plurality of diffuserhousing mounting hole apertures 282. Baffle members 90 may also beemployed in this embodiment.

As best seen in FIGS. 8, 9 and 10, included with the diffuser conduitassembly 300 is an arced mounting plate 360 if the alternativetubuluarly shaped diffuser housing 230 is employed. The arced mountingplate 360 includes a first side 362 and a second side 364. Disposedwithin the arced mounting plate 360 is a plurality of mounting plateapertures 366. The mounting plate apertures 366 are provided to receivea nut and bolt combination (not shown) or other commonly known in theart fastening mechanisms.

As viewed in FIGS. 11, 12, and 13, in another embodiment, the diffuserconduit 102 may extend through the mounting plate 160 at a predeterminedangle.

As seen particularly in FIG. 14, in still yet another embodiment, thediffuser conduit assembly 400 may be essentially linear and enter thediffuser housing 230 at a curved portion of the diffuser housing 430.

Referring to FIG. 15, in an alternative embodiment, the diffuser housing30 may also include at least one increase in cross sectional flow area170 as measured in a direction substantially perpendicular to thedirection of flow, between the diffuser housing 30 inlet end 32 andoutlet end 34. As well, the diffuser housing 30 may also include atleast one decrease in cross sectional flow area 172, again as measuredin a direction substantially perpendicular to the direction of flow,between the diffuser housing 30 inlet end 32 and outlet end 34.

Referring now to FIG. 16, in yet another embodiment, the tubulardiffuser housing 230 may also include at least one increase in crosssectional flow area 370 as measured in a direction substantiallyperpendicular to the direction of flow, between the diffuser housing 230inlet end 232 and outlet end 234. As well, the diffuser housing 230 mayalso include at least one decrease in cross sectional flow area 372,again as measured in a direction substantially perpendicular to thedirection of flow, between the diffuser housing 230 inlet end 232 andoutlet end 234.

Method of Operation

With the structure of the distribution system 20 described, adescription of the operation of the distribution system 20 will now beprovided.

In order to simplify the disclosure, several elements or means that canreadily be supplied by those skilled in the art have been omitted fromthe Figures. Such elements may include super absorbent material supplymeans, fluff generator and supply means, vacuum supply means, absorbentcore forming means, absorbent core takeaway means, controlling means,and the like. It should be readily appreciated, however, that thepresent invention can be configured and employed to produce absorbentstructures in conjunction with a variety of different machinerycomponents, and the absorbent structures can be incorporated intovarious types of absorbent articles, such as diapers, feminine careproducts, incontinence garments, bandages, absorbent pads and the like.

As best seen in FIGS. 2 and 3, a predetermined amount of super absorbentmaterial 22 with a predetermined velocity (dependent on the size of thematerial) and entrained in an air stream is supplied to the inlet end104 of the diffuser conduit 102 by any delivery means commonly known inthe art. Preferably at the same time, a predetermined amount ofabsorbent fluff 26, also with a predetermined velocity and entrained inan air stream, is supplied to the inlet end 32 of the diffuser housing30 by any delivery means commonly known in the art. The super absorbentmaterial 22 takes on a flow path 24 while the absorbent fluff 26 alsotakes on a flow path 28.

As the super absorbent material 22 streams through the diffuser conduit102, its velocity is increased when it passes through the diffuserventuri 110. The super absorbent material 22 is then blasted out thediffuser conduit 102 outlet end 106 and into the peak 122 and outersurface 124 of the cone shaped super absorbent barrier 120.

At the same time, the stream of absorbent fluff 26 is blasted throughthe diffuser housing 30 and into the peak 142 and outer surface 144 ofthe cone shaped fluff material barrier 140. Because the super absorbentmaterial 22 is blasted into the super absorbent barrier 120 and fluffflow path 28 in an opposite direction to that of the fluff flow path 28,the super absorbent material 22 slows down, then it stops, changesdirection, and now flows with the absorbent fluff 26, taking on acombined flow path 29 of super absorbent material 22 and absorbent fluff26. The invention does not blow the super absorbent material 22 into thesame direction as the fluff flow path 28 as is done in many prior artdevices.

As the combination of super absorbent material 22 and absorbent fluff 26stream through the diffuser housing 30, they preferably encounter bafflemembers 90 which disrupt the air stream and the combined flow path 29,further distributing the super absorbent material 22 and fluff 26 inorder to create the homogenous distribution.

With further regard to baffle members, in FIGS. 1 and 7, in still yetanother embodiment, baffle members 90 may be secured to a wall 40, 50,60, 70, 230, of the diffuser housing 30 or 230.

With further reference to FIGS. 15 and 16, in an alternative embodiment,the diffuser housings 30 and 230 may include at least one increase incross sectional flow area 170 and 370, and may also include at least onedecrease in cross sectional flow area 172 and 372. These increases anddecreases in flow area act as venturis to alter the velocity of theabsorbent fluff 26 as it enters the diffuser housings 30 and 230, and toalter the combined super absorbent material 22 and absorbent fluff 26 asit exits the diffuser housings 30 and 230, allowing for a more uniformdistribution. The increases and decreases in flow area also act todisrupt the flow stream, again improving the distribution of superabsorbent material 22 and fluff 26.

As further illustrated in the views of FIGS. 1, 2, and 3, absorbentfluff 26 enters the diffuser housing 30 inlet end 32, super absorbentmaterial enters the diffuser conduit 102 inlet end 104, and a homogenousmixture of super absorbent material 22 and fluff 26 exit the diffuserhousing 30 at the outlet end 34. To achieve the objective of homogenousblending, it is necessary to inject the super absorbent material 22 intothe oncoming air stream path 28 that carries the fluff 26. Thehomogenous mixture is then entrained in the combined air stream 29 tothe deposition molds commonly used in the art that form the absorbentcores.

The method for homogenous distribution according to this inventionpreferably comprises the steps of:

a. delivering a stream of super absorbent material 22 and air into theinlet end 104 of a diffuser conduit 102 in order to create a superabsorbent stream;

b. delivering a stream of absorbent fluff 26 and air into the inlet end32 of a diffuser housing 30 in order to create an absorbent fluffstream;

c. entraining the super absorbent 22 stream in the air;

d. entraining the absorbent fluff 26 stream in the air; and

e. directing the super absorbent 22 stream toward a cone shaped superabsorbent barrier 120 and directing the absorbent fluff 26 stream towarda cone shaped fluff barrier 140 so as to inject the super absorbentmaterial 22 into the absorbent fluff 26 stream at an opposite directionto that of the absorbent fluff 26 stream, thereby creating a homogenousstream of super absorbent material 22 and fluff 26.

The foregoing is considered as illustrative only of the principles ofthe invention. Furthermore, since numerous modifications and changeswill readily occur to those skilled in the art, it is not desired tolimit the invention to the exact construction and operation shown anddescribed. While the preferred embodiment has been described, thedetails may be changed without departing from the invention.

1. A method of producing a homogeneous distribution of super absorbentmaterial throughout an absorbent core, the method comprising:introducing an absorbent material into an air stream, said air streamand said first material traveling in a first direction; introducing asuper absorbent material into said air stream, said second materialintroduced in a direction opposite said first direction.
 2. A method ofproducing a homogeneous distribution of super absorbent materialthroughout an absorbent core, the method comprising: introducing astream of super absorbent material into an inlet end of a diffuserconduit; introducing a stream of absorbent fluff into an inlet end of adiffuser housing; directing the super absorbent stream toward a firstbarrier and directing the absorbent fluff stream toward a second barrierso as to inject the super absorbent material into the absorbent fluffstream at an opposite direction to that of the absorbent fluff stream.3. A distribution system for homogenous distribution of super absorbentmaterial throughout an absorbent core, the distribution systemcomprising: a housing carrying a stream of absorbent fluff in a firstdirection; a conduit carrying a stream of super absorbent material in asecond direction, said conduit coupled with said housing, said conduitdischarging said super absorbent material into said housing, said superabsorbent material decelerating in said housing, and changing directionfrom said second direction to said first direction.
 4. A distributionsystem according to claim 3, said system further comprising a pluralityof baffle members for disrupting the flow of an air stream within saidhousing for distributing the super absorbent material within theabsorbent fluff.
 5. A system according to claim 3, said conduitcomprising a diffuser conduit having an inlet end and an outlet end, thediffuser conduit having an arc bend.
 6. A system according to claim 5,said system further comprising a venturi in said diffuser conduit.
 7. Adistribution system according to claim 3, said system further comprisinga fluff barrier coupled to said housing to deflect said stream ofabsorbent fluff from entering said stream of super absorbent material insaid second direction.
 8. A distribution system according to claim 7,said fluff barrier conically shaped.